Joist and structural glossary

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Are extra items that can be furnished in addition to the base joist or joist girder. They include: headers, top chord extensions, extended ends, ceiling extensions, bottom chord extensions, sloped end bearings, bridging, bridging anchors, joist girder bottom chord bracing, or angle units (joist substitutes).


Abbrevation for 'After Dead Load is Applied'.

Alignment Chart for Columns

A nomograph for estimating the effective length factor, K, of columns in an unbraced frame. Note that the chart is based upon assumptions of idealized conditions which seldom exist in real structures.


A measure of floor vibration. It is the magnitude or total distance traveled by each oscillation of the vibration.

Amplification Factor

A multiplier of the value of moment or deflection in the unbraced length of an axially loaded member to reflect secondary values generated by the eccentricity of the load.

Anchor Bolt

A long 'L' shaped bolt which is set in concrete and used to anchor columns or other members to a foundation or other support.

Anchor Bolt Plan

A plan view showing the size, location, and projection of all anchor bolts.


The process of fastening a joist or joist girder to a masonry, concrete, or steel support by either bolting or welding.


A hot rolled shape called an Angle with symbol L which has equal legs or unequal legs.


The highest point on a joist or joist girder where the sloped chords meet. See also Peak.

Approval Plans

Plans sent by the joist manufacturer to the buyer, engineer, architect, contractor or other person for approval. The plans may include a framing plan, elevations, sections, and a material list.

ASD (Allowable Stress Design)

A structural design method whereby a structural element is designed so that the unit stresses computed under the action of working or service loads do not exceed specified allowable values. See Working Stress Design and Elastic Design.

Aspect Ratio

For any rectangular configuration, the ratio of the lengths of the sides.

Automatic Welding

A welding procedure using a machine to make a weld.

Auxiliary Load

Any dynamic live loads such as cranes, monorails, and material handling systems.

Axial Force

A force tending to elongate or shorten a member.

Axial Compression

An axial force causing compression in a member.

Axial Load

A load whose line of action passes through the centroid of the member's cross-sectional area and is perpendicular to the plane of the section.

Axial Strut Load

A structural member designed to transfer a axial tension or compression load only.

Axial Tension

An axial force causing tension in a member.

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Backing Bar

A welding aid used to prevent melting through of a joint when preforming, for example, a complete-joint penetration groove weld.

Ballast Roof

A roof which has selected material, such as crushed stone, placed on its surface to hold down the roof from wind forces.


A square or round piece of solid steel which is usually 6 inches or less in width.

Base Metal

The metal to be welded or cut.

Base Plate

A steel plate welded to the base of a column which distributes the column loads over an area of foundation large enough to prevent crushing of the concrete and usually secured by anchor bolts.


Any floor below the first story in a building.


A small piece of angle or plate welded to the heels of a two angle web member or any two parallel components to tie them together and usually located at the middle of the member.


The distance between the main frames of a building.

Base Ply

Is one layer of felt fastened to the deck over which a built-up roof is applied.

BBC (Basic Building Code)

A minimum model regulatory code for the protection of public health, safety, welfare and property by regulating and controlling the design, construction, quality of materials, use, occupancy, location and maintenance of all buildings and structures within a jurisdiction.


A structural member, usually horizontal, whose main function is to carry loads transverse to its longitudinal axis. These loads usually cause bending of the beam member. Some types of beams are simple, continuous, and cantilever.


A structural member whose main function is to carry loads both parallel and transverse to its longitudinal axis.


1) The distance that the bearing shoe or seat of a joist or joist girder extends over its masonry, concrete, or steel support 2) A structural support, usually a beam or wall, that is designed by the specifying professional to carry reactions to the foundation

Bearing Plate

The steel plate used for a joist or joist girder to bear on when they are supported by masonry or concrete supports. This plate transfers the joist reaction to the supporting structure and must be sized accordingly.

Bearing Wall

A wall which is supporting any vertical loads i2n addition to its own weight.

Bending Moment

The condition in the analysis of the internal stresses across the cross section of a member when it is subjected to forces which cause it to bend.

Bending Stress

Is zero at the neutral axis and assumed to increase linearly to a maximum at the outer fibers of the section.
Formula in the elastic range: Bending stress (in psi)=(M * c)/I, where 'M' is the bending moment at the section in in-lbs, 'I' is the moment of inertia of the section in inches^4, and 'c' is the distance from the neutral axis to the point at which the stress is desired in inches.


The plane of beam or joist girder members which support loads and the columns which support these members.

Bevel Cut

A single cut made at an angle to the member length. See Miter Cut.

BG-Type Joist Girder

A type of Joist Girder where joists are located at all panel points where vertical webs and diagonal webs intersect the top chord.

Biaxial Bending

Bending of a structural member about two perpendicular axes at the same time.


The phenomenon whereby a perfectly straight member may either assume a deflected position, deflect then twist out of plane, or may remain in an undeflected configuration.

Bill of Lading

A list that gives each part or mark number, quantity, length of material, total weight, or other description of each piece of material that is shipped to a jobsite. The receiver compares each item on this list to what is on the truck and signs the statement. See also Shipping List.

Bill of Materials

A list of items or components used for fabrication and accounting purposes. See Cut-List.


A method of cleaning or of roughening a surface by a forceable stream of sharp angular abrasive.

Blue Print

Also called a blue line. Is a copy of an architectural or other drawing made by a special machine usually on white paper with the lines and text being a blue color.

BOCA (Building Officials and Code Administrators International, Inc.)

A minimum model regulatory code for the protection of public health, safety, welfare and property by regulating and controlling the design, construction, quality of materials, use, occupancy, location and maintenance of all buildings and structures within a jurisdiction. Its serves primarily the North Central and Northeast United States.

Bolted Splice

The connection between two structural members joined at their ends by bolting to form a single, longer member.

Bond Beam

The top course of block of a masonry wall filled with concrete and reinforcing steel and used to support roof loads.

Bottom Bearing

A bearing condition where the joist or joist girder bears on its bottom chord and not at an underslung condition.

Bottom Chord

The bottom members of a joist or joist girder.

Bottom Chord Extension (BCX)

The two angle extended part of a joist bottom chord from the first bottom chord panel point towards the end of the joist.

Bottom Chord Strut

A bottom chord of a joist or joist girder designed to transfer a axial tension or compression load.

Boundary Condition

An idealization to model how a structure is attached to its "external" points of support, for example, pin, fixed, roller, or shear release.

Bow String Joist

A non-standard type of joist where the top chord is curved and the bottom chord is straight or level.

Bow's Notation

Used in a graphical analysis of a joist or joist girder. It is a notation for denoting truss joints, members, loads, and forces. Capital letters are placed in the spaces between truss members and between forces. Each member and load is then designated by the letters on opposite sides of it.

Braced Frame

A frame which resists lateral loads by the use of diagonal bracing, K-braces, or other system of bracing.


A structural support attached to a column or wall on which to fasten another structural member.

Bridge Crane

A lifting system which has a hoist that moves laterally on a beam or other member which then in turn moves longitudinally on a runway made of beams and rails.


In general, is a member connected to a joist to brace it from lateral movement. See Horizontal Bridging and Diagonal Bridging.

Bridging Anchor

An angle or bent plate attached to a wall where the bridging will be attached or anchored, either by welding or bolting. The ends of all bridging lines terminating at walls or beams shall be anchored thereto.

Bridging Clip

A small piece of angle or plate with a hole or slot that is welded to the top and bottom chord angles so that bridging may be attached.

Bridging Diagram

A diagram of the profile of a joist used to show the number and location of the rows of bridging.

Brittle Fracture

The tearing or splitting of a member with little or no prior ductile deformation.

BTU (British Thermal Unit)

The amount of heat required to raise the temperature of one pound of water by one degree farenheit.

Buckling Load

The load at which a straight member under compression transfers to a deflected position.


Any structure used for support or for shelter.

Building Code

Regulations established by a recognized agency describing design loads, procedures, quality of materials, and construction details for buildings for the protection of the public.

Building Designer

A registered architect or registered engineer who is responsible for the design of a structure. See Specifying Professional.

Building Official

The officer or other authority which has the duty of administration and enforcement of a building code.

Built-Up Roof

A type of roof composed of two or more layers of alternating felt, tar and asphalt.

Built-Up Section

A structural member made up from individual flat plates welded together or any structural metal elements that are welded or bolted together.

Butt Plate

The end plate of a structural member usually used to rest or butt against a like plate of another member in forming a connection.

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